Do-It-Yourself E85 Ethanol Test

Car Craft has been doing tech stories on E85 fuel longer than any other performance-car magazine. By now it should be well known, but in case this is news to you, E85 is an alcohol-based fuel blend of 85 percent grain alcohol and 15 percent gasoline. The idea is to create a renewable-resource fuel distilled mainly from sugarcane, corn, and/or switchgrass, which not only reduces our dependency on foreign oil but also delivers an outstanding 105-octane rating. Those are race-gasoline octane numbers. According to E85.com, across the nation, the average price for E85 is $3.12 per gallon. No, that’s not a misprint—we’re talking alcohol race gas for barely more than $3 per gallon. In Southern California, we always pay more, with the price around $3.60 per gallon. Sure, you will use 20 to 30 percent more fuel than gasoline because of alcohol’s lower energy content per gallon, but so what? This is 100-plus octane fuel for $3 per gallon. We’ll save the “Here’s What You Have to Do to Run E85 on the Street” story for a later date. For now, it’s important to understand that even though the yellow pump proclaims the fuel is 85 percent alcohol, it doesn’t mean that’s exactly what you’re getting. Often, the blend can vary between E75, E80, or E85. While this isn’t a huge issue, it will affect tuning. This happens more often during colder months, when winter blends increase the percentage of gasoline (E75, for example), which makes it is easier to initiate combustion.

E85 Ethanol Test

So how do you know what you’re getting when you pull up to the corn pipeline pump? That’s easy. Quick Fuel Technology is one of the companies leading the E85 charge with its ethanol-compatible carburetors. It also sells a simple ethanol test tube (PN 36-E85, $15.71, Summit Racing) for checking the ratio of alcohol to gasoline. The ethanol test procedure couldn't be simpler. Add water to line at the bottom of the tube, then add E85 fuel to the top line, screw the lid on the tube, and shake vigorously. Allow the tube to sit vertically for about a minute, as this will allow the alcohol to mix with the water while the lighter gasoline will rise to the top. The separation line between the alcohol/water and the gasoline will be the percentage of alcohol. In our case, the fuel checked out at slightly more than 85 percent ethanol. The ethanol test is simple and easy and is mainly used for peace of mind and comparative testing. It won’t tell you what the octane rating is, but we’ve run it on small-blocks with 10:1 static compression and 9 psi of boost with no problems, so it’s a great, high-octane fuel that costs about the same as regular pump gas.